We propose to continue our studies of acetylcholinesterase, an important nervous system enzyme, in Drosophila melanogaster as a probe of eukaryotic gene organization. Our approach emphasizes utilization of the powerful genetic technology available in Drosophila as a way of generating interesting structural and regulatory mutations, and to facilitate studies at the molecular level. We intend to identify a variety of classes of mutants affecting acetylcholinesterase, and characterize their genetic and enzymatic properties. We will study the protein chemistry of Drosophila acetylcholinesterase, with particular emphasis on the subunit organizations of the multiple forms of this enzyme. Antisera to acetylcholinesterase will be recovered and extensively used in assays for acetylcholinesterase cross-reacting material. Complete analysis of this system requires an examination of the physical organization of the acetylcholinesterase structural gene. Utilizing recombinant DNA technology, we will screen for cloned Drosophila DNA fragments corresponding to all or part of the acetylcholinesterase structural gene. We will integrate the information obtained by genetic procedures with data and material derived from biochemical and molecular biological studies to develop a detailed picture of the control of this enzyme.